This invention relates to treadmills with trampoline-like surfaces and, more particularly, to an improved mat or belt which eliminates the use of springs normally used for imparting the necessary resiliency for such an apparatus.
Treadmills utilize an endless moving belt that allows an individual to walk, jog or run in place. Treadmills are useful not only for exercise, but for rehabilitation programs and medical testing such as the "stress test" which is commonly used. There is a demand for treadmills in indoor health clubs since many clubs are not able to build a running track and a treadmill provides the capability of a well-rounded exercise program.
Most treadmills are formed with a thin, endless belt which travels over a supporting surface so that the belt can withstand the weight of the individual using it. It has been found that for these types of devices, the belt has a tendency to wear because of frictional contact between the supporting surface and the belt. Further, the rigid surface beneath the belt can cause shin splints or other stress-related injuries to the legs of the user. The value of treadmills of this design is limited for rehabilitation purposes because of the impact on the legs of the users.
It has been found that a treadmill which utilizes a trampoline-like surface with a built-in resiliency reduces impact on the legs of the users to the point where such a machine can be used as a primary therapeutic aid for rehabilitation from leg injuries. Such a treadmill is also useful for normal exercise because it significantly reduces the wear and tear on the legs of the user.
U.S. Pat. No. 4,548,405, which issued on Oct. 22, 1985, is directed to such an apparatus where a treadmill is shown and described which has a trampoline-like surface for providing the advantages described above. That machine has an endless belt which is connected along its edges through a series of springs to carrier rails located outwardly of both edges of the belt. The springs and associated carriers would move along the rail and allow the mat surface to move as the runner was exercising on the treadmill. The springs would impart a resiliency to the belt and lessen the impact on the legs of the runner using the machine.
An improved design for the treadmill with the trampoline-like surface was shown and described in U.S. Pat. No. 4,938,473 which issued on Jul. 3, 1990. In that patent, a number of improvements were described, including the use of a pair of springs spaced at an angle between each carrier and the belt in order to provide greater lateral support and stability for the belt.
It has been found that belts which utilize springs, even with the improved design shown in U.S. Pat. No. 4,938,473, have a tendency to be unstable and cause troublesome wear in that when a runner is using the machine the springs will flex unevenly at various points along the length of the belt. Further, springs have been found to add additional weight and expense to the machine itself. While the machine shown in the two patents mentioned above has proven to be successful, it was felt that elimination of the spring would improve the structure and performance of the apparatus.